New England Patriots quarterback Tom Brady's four-game suspension is "grossly inconsistent" with the NFL's previous disciplinary treatment of similar alleged conduct and based on insufficient evidence, the union representing Brady said.

"Mr. Brady’s discipline is premised solely upon the Wells report, which contains insufficient evidence to find that Mr. Brady committed any violation of NFL rules," National Football League Players' Association General Counsel Tom DePaso wrote in a letter to the NFL.

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"No player in the history of the NFL has ever received anything approaching this level of discipline for similar behavior," the letter said.

League-appointed investigator Ted Wells found that Brady was "at least generally aware" of plans by two team employees to prepare the balls to his liking, below the league-mandated minimum of 12.5 pounds per square inch.

The union countered by saying that the report is wrought "with unsupported speculation regarding Mr. Brady’s purported knowledge" of the deflated footballs.

The league's collective bargaining agreement stipulates that the appeal will be decided by NFL Commissioner Roger Goodell or a person whom he designates. Goodell has decided to hear the appeal himself.

Nonetheless, the union which has promised to call Goodell as a witness in the appeal hearing, asked Goodell to recuse himself from serving as the hearing officer.

"If the commissioner does not appoint such a neutral arbitrator, the NFLPA and Mr. Brady will pursue all available relief to obtain an arbitrator who is not evidently partial," the letter said.

The union also said it will call league vice president Troy Vincent, who handed down the punishment.

In Brady's appeal, the league will go against an experienced foe in labor lawyer Jeffrey Kessler, who has won other appeals against the league and is helping the quarterback.